Current porcine reproductive and respiratory syndrome virus (PRRSV) vaccines are not adequately effective for control and eradication of porcine reproductive and respiratory syndrome (PRRS). The main limitation of the current PRRSV vaccines is their sub-optimal coverage against divergent PRRSV strains. Thus far, all commercial PRRSV vaccines are formulated using natural PRRSV strains, but the substantial genetic variation among the PRRSV strains is the biggest obstacle for the development of a broadly protective PRRSV vaccine.